U.S. patent number 5,166,789 [Application Number 07/887,384] was granted by the patent office on 1992-11-24 for geographical surveying using cameras in combination with flight computers to obtain images with overlaid geographical coordinates.
This patent grant is currently assigned to Space Island Products & Services, Inc.. Invention is credited to E. L. Myrick.
United States Patent |
5,166,789 |
Myrick |
November 24, 1992 |
Geographical surveying using cameras in combination with flight
computers to obtain images with overlaid geographical
coordinates
Abstract
An earth surface surveying system uses an IR camera to obtain IR
images of a selected area. A video camera operates in association
with the IR camera to obtain video images in geographic and time
sequence with images obtained by the IR camera. A processor allows
split-screen viewing of the IR and video images so that areas of
interest in the IR image can be identified from the video image.
The system also includes apparatus for overlaying earth surface
coordinates on the images from a global navigation system to enable
identifying the location of areas in the images.
Inventors: |
Myrick; E. L. (Merritt Island,
FL) |
Assignee: |
Space Island Products &
Services, Inc. (Merritt Island, FL)
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Family
ID: |
27410303 |
Appl.
No.: |
07/887,384 |
Filed: |
May 21, 1992 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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662766 |
Feb 28, 1991 |
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398600 |
Aug 25, 1989 |
5045937 |
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Current U.S.
Class: |
348/144; 348/164;
348/E7.085 |
Current CPC
Class: |
G01V
9/00 (20130101); H04N 7/18 (20130101) |
Current International
Class: |
G01V
9/00 (20060101); H04N 7/18 (20060101); H04N
007/18 () |
Field of
Search: |
;358/109,110,103,113,183,83 ;364/443,449 ;340/727,922-925 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Ljunberg; "Aerial Thermography-Cartographic Presentation of
Thermographic Data for Building Applications"; SPIE-The
International Society for Optical Engineering Proceedings; Mar.
29-31, 1989; vol. 1094; pp. 13-22. .
Safabakhsh; "Processing Infrared Images for High Speed Power Line
Inspection"; SPIE-The International Society for Optical Engineering
Proceedings; Mar. 29-31, 1989; vol. 1094; pp. 75-82..
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Primary Examiner: Kostak; Victor R.
Attorney, Agent or Firm: Beusse; James H.
Parent Case Text
This application is a continuation of application Ser. No.
07/662,766 filed Feb. 28, 1991 now abandoned which is a
continuation-in-part of application Ser. No. 07/398,600, now U.S.
Pat. No. 5045,937.
Claims
What is claimed is:
1. An earth surface survey system for mounting in a survey vehicle
comprising:
a video camera having a first field of view, said camera producing
a sequence of television frames of a portion of an earth surface
within a field of view of said camera;
video recorder means connected to said video camera for recording
said sequence of television frames;
a global navigation system for determining coordinates of said
survey vehicle;
a computer for receiving said coordinates from said global
navigation system and programmed to produce alphanumeric
representations thereof; and
means connected to said computer and said video recorder means for
overlaying respective determined coordinates on each of said
television frames.
2. The survey system of claim 1 which further comprises: radar
altimeter means for measuring the height of said vehicle above said
portion of earth surface; and
said computer programmed to produce alphanumeric representations of
said measured heights for overlaying on each of said television
frames.
3. The survey system of claim 1 which further comprises a second
video camera having a second field of view wider than said first
field of view and including said first field of view, said second
video camera producing a second sequence of television frames.
4. The survey system of claim 3 which further comprises second
video recorder means connected to said second video camera for
recording said second sequence of television frames.
5. An aerial infrared earth surface survey system for mounting in
an aircraft comprising:
an infrared imager head having a narrow angle field of view, said
imager head producing analog data representative of temperatures of
infrared sources in said imager head field of view;
an infrared data processor connected to receive said infrared
analog data for processing said data to produce a sequence of
television frames in which colors of images therein are indicative
of a temperature range of said infrared sources corresponding to
said images;
first video recorder connected to receive and record said sequence
of television frames;
a global navigation system for determining the latitude and
longitude of an aircraft carrying the survey system;
a radar altimeter for determining the height of said aircraft above
an earth surface;
a computer for receiving latitude and longitude data from said
global navigation system, and aircraft height data from said radar
altimeter, said computer programmed to produce alphanumeric
representations of said received latitude and longitude data, and
said height data; and
a time base corrector connected to receive a synchronization signal
from said data processor and to receive and alphanumeric
representations for overlaying representive latitude, longitude,
and height alphanumeric representations on each of said television
frames for recording by said first video recorder.
6. The survey system of claim 5 which further comprises:
a pod for mounting said infrared imager head;
means for mounting said pod in said aircraft such that said pod is
pivotable along a longitudinal axis of said aircraft; and
a control stick operatively associated with said pod for enabling
an operator to roll said pod for tracking of earth surface
features.
7. A method for locating points of interest on the earth's surface
by temperature discrimination comprising the steps of:
moving an infrared imager head along and over selected areas of the
earth's surface for scanning such areas;
producing a sequence of infrared television frames from the
infrared imager head having images representative of temperatures
of the area scanned;
determining coordinates of centers of the selected areas in each of
the television frames;
overlaying the determined coordinates of each frame on its
respective recording thereof;
playing back the recording to locate a thermal point of interest in
the infrared portion of a frame;
visually identifying the location of the thermal point of interest;
and
determining the location of the thermal point by reference to the
overlaid coordinates of a frame containing the thermal point of
interest.
8. An infrared earth surface survey system for mounting in a survey
vehicle comprising:
an infrared camera for producing a sequence of infrared images of a
portion of an earth surface within a field of view of said
camera;
an infrared data processor connected to said infrared camera for
receiving analog infrared data therefrom, said processor processing
said infrared data to produce a sequence of infrared video frames,
said processor producing a plurality of colors in said frames, each
of said colors indicative of a temperature range of a portion of an
earth surface within said camera field of view;
video recorder means connected to said data processor for recording
said sequence of video frames;
a global navigation system for determining coordinates of said
survey vehicle;
a computer for receiving said coordinates from said global
navigation system and programmed to produce alphanumeric
representations thereof; and
means connected to said computer and said video recorder means for
overlaying respective determined coordinates on each of said video
frames.
Description
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to infrared surveys of geographical
areas and, more particularly, to an improved survey system and
method using infrared and color television images and having means
for determining and recording coordinates of points of interest of
the survey.
2. Description of the Prior Art
Geographical surveys utilizing infrared sensors are extremely
useful for a number of activities. For example, such surveys are
applicable to detection of gas pipeline links; detection of
problems in electric power transmission lines; determining the
density of populated areas; search and rescue missions; pollution
studies; and timber surveys. Infrared detection systems provide
information concerning areas having a distinct temperature
differential from the background temperatures and use of such
systems for surveys is known in the art. However, a major problem
in such surveys that has not been adequately solved is accurate
determination of the location of small ground features detected by
an infrared system.
A typical prior art infrared survey system is disclosed by Dibbero,
U.S. Pat. No. 3,076,961. An airborne multiple sensor system is used
having an infrared camera, a television camera, and a radar
scanner. The multiple sensors provide detection and identification
of camouflaged targets such as required in military operations. No
means for producing accurate ground coordinates of detected targets
is provided. Parker et al., in U.S. Pat. No. 3,752,915, teach
recording on magnetic tape of thermal ground and reference data
obtained from an airborne scanner to produce color images. U.S.
Pat. No. 4,516,158 to Grainge et al. shows two airborne infrared
scanners that scan in different directions.
None of the above systems provide accurate identification of ground
coordinates, such as latitude and longitude, of located targets nor
altitude from which the survey was made. Therefore, a need remains
for an accurate survey system utilizing infrared scanning, color
video, and video recording that includes means for recording the
latitudes and longitudes of small areas of interest located during
the survey. For aerial surveys in which a system provides latitude
and longitude coordinates, which provides means for locating the
coordinates with a ground vehicle is required.
SUMMARY OF THE INVENTION
The present invention utilizes a camera pod having two color video
cameras and an IR imager head. For aerial surveys, the pod may be
mounted below the fuselage of a fixed wing aircraft or helicopter.
The IR imager head includes a plurality of infrared detectors
supplied with cryogenic cooling and means for scanning the
detectors over a field of view directly downward from the aircraft.
The two video cameras cover essentially the same field of view as
the IR imager with one camera having a normal field of view and the
other camera having a wide angle view. The analog infrared data
from the IR imager head is transmitted to an IR data processor
which converts the data to a standard NTSC color television frame.
The resolution of the imager provides sixteen levels of color
indicative of the temperatures in the scene. The IR data processor
produces a master composite sync signal to which the two video
cameras are slaved or "genlocked". The video signal from the normal
field of view camera and the color television signal from the IR
data processor are fed to a special effects generator which
produces a split screen in which an upper portion of the screen
displays the color IR image of a forward frame and the lower
portion of the screen displays the color video image from the video
camera of the following portion of that frame. The wide angle video
camera output is recorded on a second video recorder and the
composite split screen image from the special effects generator is
recorded on a first video recorder. The video recorders each
operate separate monitors by which the operator may observe the
scenes being recorded.
Advantageously, the split screen technique permits a playback of
the recorded images to allow any anomaly, or point of interest
appearing in the forward infrared portion of a frame to be tracked
into the color video portion of a following frame. Slow motion or
stop-frame playback thereby permits analysis of the point as to the
source of the infrared data.
To accurately locate points of interest in the recorded scenes, a
global position system (CPS) is provided and connected to an
external antenna. A computer receives the output from the CPS on
its RS-232 input and is programmed to produce latitude and
longitude information in alphanumeric form therefrom which is
superimposed and recorded on each frame of the two video recorders
along with the scenes from the video and IR cameras being recorded
thereon. When the system is used in an aircraft, a radar altimeter
is provided with an output connected through the game port or
analog to digital output port of the computer to generate the
altitude alphanumeric information which is also superimposed on the
video recorder frames.
The altitude and latitude and longitude information along with the
known lens angle permits distances in each frame on the monitor to
be scaled and the coordinates of any points of interest to be
accurately determined during playback.
The aircraft communication equipment audio outputs are fed to the
audio inputs of the video recorders, such that operator comments
and other useful audio information may be recorded
contemporaneously with the video recordings.
To permit on-ground surveys, the system may be installed in a
rugged terrain vehicle with the camera pod mounted on the roof.
When an aerial survey is made, a GPS may be installed in a ground
vehicle to be able to locate points of interest found during the
survey at specific latitude and longitude coordinates. In difficult
terrain, hand carried equipment may be used.
Advantageously, the survey system invention is suitable for
locating leaks in gas pipelines, locating lost personnel, air
search and rescue, detecting hot spots in electric power
transmission systems, and similar applications where a point of
interest is at a different temperature than the surroundings.
It is therefore a principle object of the invention to provide a
survey system having color video cameras and an infrared imager to
permit recording of color images of the area being surveyed
simultaneously with infrared images in a color display in which the
colors indicate the temperatures of various portions of the scene,
and including a GPS which simultaneously produces readings of the
latitude and longitude of the area being surveyed.
It is another object of the invention to provide an infrared and
color video survey system capable of being mounted in an aircraft
in which a GPS and a radio altimeter are connected to superimpose
latitude and longitude readings and altitude readings on video
recordings of the surveyed territories.
It is still another object of the invention to provide an infrared
and color video surveying system for geographical areas in which a
split screen display showing both the infrared scene and the
adjacent color video scene on a monitor is provided.
It is still another object of the invention to provide an infrared
and color video survey system in which points of interest in the
areas surveyed can be located by their latitude and longitude, and
in which such system may be mounted in an aircraft or on a ground
vehicle.
It is still another object of the invention to provide an infrared
and color video surveying system for geographical areas in which
points of interest in the areas surveyed can be located by their
latitude and longitude recorded on each frame by scaling the frames
as viewed in the monitor, and which system can be mounted in an
aircraft or ground vehicle.
It is a further object of the invention to provide a system for
producing hard copy survey information on video tape, which can be
retained by a pipeline or powerline owner as proof of survey, and
referred to for maintenance or for future reference.
These and other objects and advantages of the invention will become
apparent from the following detailed description when read in
conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a survey system in accordance with the
invention adapted for use in an aircraft;
FIG. 2 is a diagram showing the field of view coverages of the two
video cameras and the IR imager head of FIG. 1; and
FIG. 3 is a typical split screen image as displayed on the monitor
of FIG. 1 and recorded by a video recorder.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The infrared survey system of the invention may be effectively used
for a variety of survey types. For the purposes of this disclosure,
the preferred embodiment will be described with reference to a gas
pipeline leak survey using either aircraft mounted or vehicular
mounted equipment. Leaks in a high pressure underground pipeline
carrying gas will result in expansion of the escaping gas producing
cooling of the surrounding soil. Therefore, a thermograph of the
area will show a thermal pattern of lower than average temperatures
and the lowest temperature will occur most often at the leak
location.
Turning now to FIG. 1, a block diagram of the survey system of the
invention for an aircraft mounted system is shown. To provide an
aerial survey, the equipment may be mounted in a fixed wing
aircraft for long distance and cross country surveys. When
operating in congested areas or difficult terrain with mountains,
the system may be carried in a helicopter. For use in an aircraft,
a camera pod 10 is provided which is pivoted along the horizontal
axis 11 of the aircraft having a control stick 13 accessible to an
operator. Control stick 13 permits the operator to roll the pod if
necessary to maintain a target in view. Pod 10 contains a normal
field of view video camera 12, referred to herein as camera 1; and
a wide angle field of view video camera 14, referred to as camera
2. Cameras 12 and 14 are preferably color cameras and each may be a
Javelin Electronics Color Camera Model JE3462HR. Cameras 12 and 14
are oriented vertically such that the ground immediately below the
aircraft is centered within the field of views of the cameras 12
and 14 which include genlock capability.
To provide the desired detection of cool areas, indicative of a
leak in the pipeline leak detection application, an infrared imager
head 16 is mounted with its field of view having the same
orientation as cameras 12 and 14. A preferred thermal video system
having an infrared imager head is the Hughes Aircraft Company Model
3100 available from Hughes Aircraft Company, Carlsbad, Calif. The
Hughes imager head has ten active elements and utilizes a
collimated beam scanning technique which optomechanically scans a
fifteen degree horizontal by a ten degree vertical field of view
with 10:1 interlace. A linear array of ten infrared detectors
converts the received IR radiation into electrical signals. The
spectral range is 2.0 to 5.6 microns. A cryogenic cooler 17
maintains the IR imager head at an operating temperature of
87.degree. K.
The signals from the ten infrared detectors in imager head 16 are
connected through appropriate amplifiers to infrared data processor
20. Data processor 20 receives the analog thermographic data
transmitted from the IR imager and converts the signals to color
thermograms of the area viewed. The color video output is
preferably the NTSC standard 525 lines at sixty frames per second.
The Model 3100 thermal video system has an observable temperature
range of -20.degree. to 950.degree. C. with a sensitivity of
0.5.degree. C. Data processor 30 produces a 200 line display
interpolated from 100 IR lines and a display level of sixteen
colors. A master composite synchronization signal is generated by
data processor 30. Keyboard 21 permits operator control of data
processor 30 as discussed hereinafter.
Data processor 20 quantizes the temperature range into sixteen
levels, corresponding to the sixteen display colors. The keyboard
21, connected to data processor 20 permits the operator to select a
desired range of temperature within the -20.degree. to 950.degree.
C. capability of the system. The selected range is provided to
first video recorder 32 and is recorded on each video frame as will
be discussed hereinbelow. The resolution of each level may be
varied from 0.1.degree. C. to 60.degree. C. thus permitting ranges
of 1.6.degree. C. to 960.degree. C. to be used, depending upon the
resolution desired. The range desired for a survey is selected via
keyboard 21. The range may be set at any point within the
temperature capability as required by the background temperature
and the expected target temperature.
It is desired to combine the video frames from normal field of view
camera 12 with the IR frames obtained from IR imager head 16 in one
display so that a pictorial view of the terrain will be presented
with the forward portion an infrared thermogram and the following
portion a color video frame, the two half-frames matched as will be
described in detail hereinbelow.
To produce properly matched frames of video infrared images, pod 10
must have the first video camera 12 and infrared imager head 16
aligned. Each must produce a full field view frame centered on the
same point; first camera 12 and imager head 16 are equipped with
lenses having the same angle of view. To this end, a special
effects generator 26 is utilized which receives the standard full
field of view video signal from the first video camera 12, and also
supplies a sync signal to that camera. Effects generator 26 also
receives the full field of view infrared video signal from data
processor 20. Effects generator 26 splits the scanning frame to
produce a split screen effect with the IR field of view in the
upper or forward half of the screen and the normal color video view
in the lower or following half.
A SciTech Special Effects Generator Model 31 is well suited for
this function and is available from SciTech of Miami, Fla. The
model 31 provides a choice of various types of split screen
displays although a horizontally divided screen is preferred for
pipeline survey. The combined infrared video from imager head 16
and color video from first video camera 12 is recorded on a first
video recorder 32. A second video recorder 36 receives video
directly from the second video camera and records the wide angle
field of view color image. The video recorders may be Cannon VR-20A
models, available from Cannon, U.S.A., Norcross, Ga. 30071.
An important element in the system is the means for determining the
ground location of features of interest observed by the system. For
example, the location of a pipeline leak indicated by the displays
is required to permit ground personnel to find the leak. A global
navigation system (GNS) 38 with external antenna 39 is utilized for
this purpose. A preferred GNS 38 is the Motorola Global Navigation
System which utilizes satellite coordinate information. This system
has the capability of locating any point on the earth's surface.
GNS 38 transmits the position information produced through an
RS-232 connecting cable to computer 30.
An alternative implementation of GNS 38 is a loran-C system, for
example, the Apollo 2 Model 612 available from II Morrow, Inc. of
Salem, Oreg. This model has a cross-tracked distance resolution of
sixty feet and can track at 650 knots at 20,000 feet. Each reading
is accurate within a few feet. Other global navigation systems
suitable for use with the invention are Norstar and Omega.
Computer 30 may be any programmable microprocessor computer. For
example, a Commodore Amiga 1000 Computer has been used. Computer 30
processes the information received at its RS-232 input from GNS 38
which is transferred through the computer RGB output to time base
corrector (TBC) 28 as latitude and longitude information. This
information is then transmitted to first and second video recorders
32 and 36 which act as the survey logs for the system. The latitude
and longitude information received from GNS 38 is overlaid and
recorded on each video frame produced in the survey logs by video
recorders 32 and 36. TBC 28 may be a SciTech "Genkey", available
from SciTech of Miami, Fla.
The audio inputs of video recorders 32 and 36 are connected to the
aircraft communication equipment 37 to record data received from
the radios, or from automated pipeline data such as pressure, rate
of flow, internal temperature, and the like which are recorded in
real time. Also, the crew can enter spoken notes of relevant
information. Video monitors 34 and 35, which may be Sony PVM-8221
monitors, are disposed directly in front of the operator of the
system and display real time images of data as recorded by first
video recorder 32 and second video recorder 36, respectively. This
allows the operator to monitor the temperature, range, and
resolution of the data from IR data processor 20, the focus of the
IR imager head, the display mode of the special effects generator
26, and the data from computer 30. This permits the operator to
change, reset, or adjust the system as necessary. Any deviation of
the aircraft from its predetermined course can be noted and
corrected. The operator may roll the camera mount 10, using control
stick 13, as necessary to track the survey route in the event of
deviation from course or aircraft roll in the presence of
turbulence.
Radar altimeter 24 is provided having a downward looking antenna
25. The signal from altimeter 24 is fed to computer 30 via a game
port and is combined with the longitude and latitude information
from GBS 38. The altitude is recorded and displayed on each frame
of the video recorders 32 and 36. Radar altimeter 24 may be a Terra
3000/TRI 30 model available from Terra Corporation, Albuquerque,
New Mexico. The TRA 3000 has an altitude range of 40 to 2500
feet.
Referring now to FIG. 2, an aircraft 5 with the system of FIG. 1
installed therein is shown with a typical longitudinal field of
view indicated for each of the three cameras. Field of view B
represents the portion of the coverage of the IR imager head 16
which is displayed, providing a thermographic view of the terrain
within that field of view. Field of view C indicates the portion of
the video color display produced by first video camera 12 of the
terrain adjacent to an following the field of view B. Field of view
A is the wide angle view of second video camera 14 which provides a
color video view of the terrain including the portions of field of
views B and C and extending a distance around such fields. For
pipeline leak detection, this may assist in locating landmarks and
the like. When the system is used for population surveys, the wide
field of view is advantageous.
A typical split screen image as produced by first video camera 12
and IR imager head 16 is shown in FIG. 3. Frame 40 has been split
such that the forward infrared image half-frame 44 appears in the
top half of the screen and the following color video image 45
appears in the lower half of the screen in accordance with the
fields of view shown in FIG. 2. The Hughes Thermo Image System also
produces a set of sixteen color samples 42 ranging from a violet on
the left through the spectrum to a white on the right to show the
temperature from cooler to warmer. The calibration and range are
indicated by number displays 43; in this example, the resolution is
0.6.degree. C. The pattern shown in the infrared display 44 has a
region 47 which appears as a dark blue with spots 46 which are
violet. The background is a light blue. As will be understood, this
indicates that 47 is a cool region with 46 being the coldest
portion thereof and would most likely indicate a leak in a gas
pipeline. The lower half-frame 45 provides a pictorial view of the
area behind and contiguous with the area of the infrared half-frame
44. Half-frame 45 shows heavy foliage with a clearing for the
pipeline right-of-way through the center. As will be understood, as
aircraft 5 proceeds, the area shown in upper half-frame 44 will be
shown pictorially as the color video image of lower half-frame
44.
During playback on the ground, the video recording may be operated
in slow motion. In the frames following frame 40 of FIG. 3. point
46 will appear to move downward into the video portion of the frame
and point 46 will appear at 46A, shown by the "X" in FIG. 3 and the
frame is then stopped. The video representation may be examined to
identify the point 46, and the exact location can be scaled from
any prominent landmark, such as a fence, ditch, roadway, or the
like. Portable tape playback equipment may be carried by ground
crews to assist in locating points of interest.
The system advantageously utilizes readily available and proven
equipment in a novel combination to provide a flexible, universal
system for infrared surveys. A number of the units basically are
used which are designed for 115 volt AC 60 Hz power, while others
are made for vehicular or aircraft use and operate from 12 V DC.
FIG. 1 illustrates a power supply 35 which may contain a high
efficiency twelve volt gel cell to provide power to the DC operated
equipment. The battery may operate an inverter to produce the 115 V
AC 60 Hz cycle required by the other equipment. A charger input is
provided to power supply 35 such that, during operation in an
aircraft or vehicle, the normal vehicle charging system may be used
to maintain the battery voltage.
In the example used to describe the invention, it is, of course,
necessary to be able to locate the points of interest found on the
ground, for example, a gas leak from a pipeline. In such instance,
a vehicle need only be equipped with a GNS receiver to be able to
locate an exact latitude and longitude indicated from review of the
recorded video and infrared images. Similarly, where surveying is
to be done on the ground, a rugged terrain vehicle may have the
complete system mounted on the vehicle. The altimeter would not be
needed. The camera pod and cameras may be shock mounted on the roof
of the vehicle with suitable means for aiming the cameras.
In operation of the system, the operator adjusts temperature range
of data processor 20 in accordance with the mission. For example,
in pipeline gas leak detection, the average low temperature
expected or observed is input by keyboard 21 as the low
temperature. The width of the temperature window is controlled by
the temperature resolution between color levels as input by the
operator. The high temperature measured on the thermogram will be
the selected low temperature input plus sixteen times the selected
resolution. The operator should adjust low temperature ranges and
resolution to conform with average temperatures as observed. This
range may vary and need to be reset due to changing terrain, amount
of reflected solar radiation, or amounts of moisture in the soil. A
gas pipeline leak may cause a colder area to be recorded showing a
pattern of progressively colder isotherms with the center of the
pipeline leak generally at the coldest point.
For search and rescue over water, the flight survey is preferably
made at night to avoid emissivity error. The water temperature plus
1.degree. F. may be input as the low temperature. Resolution is set
to a minimum, for example, 0.2.degree. F. producing a temperature
envelope of only 3.2.degree. F. Special effects generator 26 is
configured to record and show on the monitor a full screen infrared
image. The screen will be blank until the survey track passes over
a person in the water. Since the person's temperature will be
greater than 4.2.degree. above water temperature, the infrared
sensor will produce a bright blip on an otherwise blank screen.
With latitude and longitude recorded, a record of position is
established and can be communicated to the Coast Guard or other
rescue forces.
As will now be understood, a survey system particularly well suited
for aerial surveying has been disclosed using infrared sensing to
identify desired ground features, and which is assembled from
readily available equipment. The system may locate points of
interest by latitude and longitude coordinates and direct scale
measurements within a few feet, thus permitting such surveys to be
performed at very low cost and in a minimum of time. Although
various specific elements of the invention have been identified by
model and manufacture, functional equivalents of such units are
available from other sources, and the invention is not to be
limited to the specified units. In addition, various modifications
may be made in the procedures hereinabove as well as the
interconnection of equipmemt, without departing from the spirit and
scope of the invention.
* * * * *